The co-use of alcohol and nicotine is positively correlated in man, with people who drink alcohol having an increased probability of smoking and vice versa. Although alcohol and nicotine are known to be one of the most common combinations of drugs abused by man, little is known about the relationship between these two drugs. The experiments proposed will examine the interaction between these drugs in rats by investigating the effect of self-administration of one drug on the subsequent self-administration of the other drug as well as the concurrent administration of both. The hypothesis being tested predicts that alcohol and nicotine are interacting by a pharmacological mechanism and that self-administration of one drug will be affected only when the other drug is present. These experiments are unique because the rats will be able to self-administer both nicotine (intravenously) and alcohol (orally) during daily operant sessions. Examination of the relationship between alcohol and nicotine using this procedure will develop a model that can be used for further determination of the mechanism of the interaction between these two drugs.